The present invention relates to a scanning electron microscope.
In recent years, attention has been focused on a scanning electron microscope (SEM) including a focused ion-beam (FIB) device. Such a scanning electron microscope includes a SEM column and a FIB column.
As disclosed in Japanese Patent Application Publication No. 2001-84951, a scanning electron microscope including a FIB device includes a secondary-electron detector which is used during both of FIB processing and SEM observation and a backscattered-electron detector which is used only during SEM observation.
The backscattered-electron detector has a high detection sensitivity to a backscattered electron having a relatively high energy. However, during FIB processing, an electron having a high energy such as a backscattered electron is not formed, and therefore observation cannot be performed using the backscattered-electron detector. Accordingly, the backscattered-electron detector is used only during SEM observation.
The secondary-electron detector can be used not only during SEM observation, but also during FIB processing. For example, secondary electrons generated from a specimen during FIB processing are detected using the secondary-electron detector, and an amount of signal resulting from the secondary electrons is illustrated as a graph or an image. The amount of signal (such as, e.g., a change in the brightness of the image) resulting from the secondary electrons allows the state of the specimen to be monitored and allows the end of the processing to be determined.
In the scanning electron microscope including the FIB device, sputtered particles generated by FIB processing are deposited in a chamber to form a deposited film. When the deposited film is formed over the detection surface of the backscattered-electron detector and it grows, the detection sensitivity of the backscattered-electron detector deteriorates.
In such an electromagnetic field as to allow an electron beam to be bent, backscattered electrons are scarcely deflected, and sputtered particles follow linear trajectories. As a result, no matter where the backscattered-electron detector is placed in a specimen chamber, as long as backscattered electrons are detected, sputtered particles are also deposited.